"Far from Xanadu", by Julie Ann Peters.
Mike lives in Coalton, a tiny town out in the middle of nowhere. Mike plays softball, works out, and loves plumbing. She's gay, too – or so her best friend Jamie insists. Mike believes him, to a point. She prefers not to think about it, and to fill her time with softball, school and work. And then a new student joins her small class. Xanadu. She's all Mike has ever dreamed of; brave, street-smart, beautiful – and also straight. As the book progresses, Xanadu becomes friends with Jamie and Mike. As Mike struggles with her secret love and her family, Jamie finds someone, too – maybe. And, sadly, so does Xanadu.
But Mike still harbors hope – until...
I can't figure out a way to hint at what happens without giving it away, so I'll just leave you with a "...". This is a wonderful book, and Julie Ann Peters writes with a grace and style that perfectly portrays Mike's mind.